The present disclosure relates to an imaging apparatus and method for imaging a transmission image of a subject to be examined by detecting light that has passed through the subject to be examined.
Conventionally, an imaging apparatus that images a transmission image of a subject to be examined set on a subject-to-be-examined support unit made of glass or the like has been proposed (please refer to Japanese Unexamined Patent Publication No. 2002-156714 (Patent Document 1) and Japanese Unexamined Patent Publication No. 2015-177250 (Patent Document 2)).
For example, in the imaging apparatus disclosed in Patent Document 1, a fluorescent plate is placed on a subject to be examined set on a subject-to-be-examined support unit. Then, the subject-to-be-examined support unit is illuminated with excitation light from a side opposite to a side on which the subject to be examined is set, and the fluorescent plate is illuminated with the excitation light that has passed through the subject-to-be-examined support unit and the subject to be examined. At this time, a part of the excitation light is absorbed by an image recorded on the subject to be examined. Therefore, the fluorescent plate is illuminated with the excitation light the light amount of which is in inverse proportion to the density of the image.
Fluorescence emitted from the fluorescent plate by illumination of the fluorescent plate with excitation light is photoelectrically detected by a detector, such as a photomultiplier, after passing through the subject to be examined and the subject-to-be-examined support unit. At this time, a part of the fluorescence is absorbed by an image recorded on the subject to be examined. Therefore, fluorescence the light amount of which is in inverse proportion to the density of the image is detected by the detector. Further, a transmission image of the subject to be examined is imaged by two-dimensionally scanning the subject to be image with excitation light and by sequentially detecting fluorescence transmitted through the subject to be examined, as described above. The transmission image imaged in this manner has a density gradation about twice as many as the image recorded on the subject to be examined.